The inventiion relates to chem-milling and, more specifically, to preparing the surface of material coated with chem-mill resistant maskant in the areas desired to be chem-milled.
The conventional method of preparing material to be chem-milled in those specific areas is to coat the surface of the material with a chem-mill resistant maskant material and then mechanically punching or drilling holes of a smaller diameter than the desired resultant diameter hole through the maskant and/or maskant and the material. This method, although highly successful for certain utilization of perforated finished material, has been found to cause an increase in the occurrence of material fatigue and to highly stress the material adjacent the hole which causes warpage of the material requiring the additional operation of flattening the material prior to use.
The problems existing in the current phase of the art have not been successfully overcome until the emergence of the instant invention.